How to read an AQL table, step by step

An AQL table is really two tables used one after the other. The first turns your lot size into a letter. The second turns that letter and your AQL into a sample size and two numbers. This page walks through both, using the tables of MIL-STD-105E.

Step 1: lot size and inspection level give a code letter

Open the code letter table (Table I). Find the row whose range contains your lot size, then read across to the column for your inspection level.

Example: a lot of 5,000 units falls in the row 3201 to 10000. Under general inspection level II that row gives the letter L.

Clause 3.21 of the standard describes the code letter as a device used along with the AQL for locating a sampling plan on a table of sampling plans. The letters run from A to R, without I or O.

Step 2: the code letter gives a sample size

Open the single sampling table (Table II-A). Each row is a code letter, and the second column is its sample size.

For L the sample size is 200.

Step 3: the AQL column gives Ac and Re

Stay on the row for your letter and move across to the column for your AQL. The cell holds two numbers:

• Ac, the acceptance number.
• Re, the rejection number.

For letter L and an AQL of 2.5 the cell reads 10 11. Ac is 10 and Re is 11.

Step 4: inspect and compare

Clause 4.10.1.1 gives the rule for a single sampling plan. Inspect a number of units equal to the sample size. If the number of defectives found is equal to or less than the acceptance number, the lot is considered acceptable. If it is equal to or greater than the rejection number, the lot is rejected.

In the example: inspect 200 units. With 10 or fewer defective units the lot is accepted. With 11 or more it is rejected.

In this table Re is always one more than Ac, so every count leads to a decision.

When the cell is an arrow

Many cells hold an arrow instead of two numbers. The legend under Table II-A explains them:

• A down arrow means use the first sampling plan below the arrow.
• An up arrow means use the first sampling plan above the arrow.

Clause 4.9.3 adds the part that is easy to miss: the sample size to be used is given by the new code letter, not by the original letter.

Two examples for a lot of 100 units at level II, which gives letter F (sample size 20):

AQL	Cell for F	Plan used	Sample size	Ac	Re
1.0	up arrow	letter E	13	0	1
1.5	down arrow	letter G	32	1	2

So with the same lot and the same level, moving the AQL from 1.0 to 1.5 changes the sample from 13 units to 32.

When classes of defects end up with different sample sizes

Because arrows can move each AQL to a different row, critical, major and minor defects can end up with different sample sizes. Clause 4.9.3 allows the code letter corresponding to the largest sample size to be used for all classes of defects.

The same clause gives one more option: instead of a plan with an acceptance number of 0, the plan with an acceptance number of 1 and its larger sample size for the same AQL may be used, where the table has one.

When the sample is as large as the lot

The footnote to Table II-A says: if the sample size equals or exceeds the lot or batch size, do 100 percent inspection.

Example: a lot of 5 units at level II gives letter A (sample size 2). At an AQL of 2.5 the cell is a down arrow, and the first plan below it belongs to letter C, with a sample size of 5. The sample equals the lot, so every unit is inspected.

Questions people ask

Do I use the sample size of my own letter after following an arrow?

No. Clause 4.9.3 says the sample size is given by the new code letter, not by the original one.

Why is there no plan for my letter and AQL?

For some combinations the standard provides no plan and the table directs you to a different letter (clause 4.9.3). That is what the arrow does.

Which table do I use if inspection is tightened or reduced?

Not this one. Table II-A is for normal inspection. MIL-STD-105E has separate master tables for tightened inspection (II-B) and reduced inspection (II-C), and clause 4.7 sets the rules for switching between them.

Source

• MIL-STD-105E, Sampling Procedures and Tables for Inspection by Attributes, U.S. Department of Defense, 10 May 1989: Table I, Table II-A with its legend and footnote, and clauses 3.21, 4.7, 4.9.3 and 4.10.1.1. Page scans: archive.org/details/MIL-STD-105E_1. Read 11 October 2026.

Where your contract names ANSI/ASQ Z1.4, ISO 2859-1 or another standard, use the tables of that edition.